1. Field of the Invention
The present invention relates to a head lamp for a vehicle such as automobiles and bicycles. More particularly, the present invention relates to a head lamp having a discharge lamp, such as metal halide lamp, used as light source that is hard to contain two light sources closely adjacent to each other for passing beam state and driving beam state.
2. Background Art
There are many applications for a head lamp 90 constructed to switch it between a passing beam state and a drive beam state with use of a discharge lamp as a light source. For example, there has been proposed the head lamp in Laid-Open Japanese Patent Application No. 8-111101. As major parts of the head lamp is shown in FIG. 7, a top of a discharge lamp 91 is held with a fulcrum 92a as an axis, a lever 92 is provided in a perpendicular direction thereof, and a burner 91a is positioned on roughly an optical axis Z as a passing beam position.
In that construction, to switch to the drive beam state, the lever 92 is moved back with the fulcrum 92a as center of turning by an actuator 94 such as a motor or a solenoid to turn the discharge lamp 91 by a specific angle a. This moves the discharge lamp 91 from the passing beam position to the drive beam position that is backward and downward relative to the reflecting mirror 93.
The head lamp 90 mentioned above can considerably increase amount of light as it uses the discharge lamp 91 as a light source, thus being effective for a driver to increase visibility. However, the passing beam of the head lamp 90 causes much dazzling even with the head lamp 90 moved little upward for oncoming cars, particularly in a road having a large amount of traffic.
To solve such a problem, there has been proposed another head lamp having an automatic leveling device used therein. Namely, to overcome a moving condition that a front portion of a vehicle may be moved up if a weight matter is put on a rear body or if starting or acceleration is made, the automatic leveling device can automatically adjust angles of elevation and depression of the reflecting mirror 93 of the head lamp 90 depending on state of a suspension, thereby preventing the illumination light from directing upward.
However, with such an arrangement, the head lamp 90 has an disadvantage that it needs such a device for automatically leveling in addition to a mechanism for switching between the passing beam state and drive beam state. In addition, the head lamp 90 is involved in such a problem that it is complicated in construction and made large size and high cost.